Magnetizable core



June 1G, 1941. A WEIS ET AL; 2,245,373

MAGNETIZABLE CORE Filed Jan. 4, 1958 Fig. 2

aiming Patented June 10, 1941 y MAGNETIZABLE CORE Adolf Weis and Gnther Drewes, Berlin-Charlottenburg, Germany, asslgnors to Siemens & Halske Aktiengesellschaft, Semensstadt, near Berlin, Germany, a corporation of Germany Application January 4, 1938, Serial No. 183,260 In Germany December 30, 1936 4 claims. (c1. iii- 242) It is not 5 magnetizable cores present `irregularities as to 10 their dimensions and structure and thereby cause departures of the inductance values from l the required values. It has already been proposed to effect in such oscillation circuits an 'addensers for the highest frequency in combination with a magnet coil which allows a compensation for the lowest frequency by varying the permeability as well as a compensation for an intermediate frequency by varying the position of the core with respect to the coil windings. Such way of compensation, `-however, does not ensure a sufciently accurate ganging of the tuned circuits as to the frequency characterjustment by employing variable tuning con- 15 istic for the ranges lying between the three compensated values. By these measures it is not possible to accurately maintain a predetermined frequency characteristic even in the case of a. simple oscillation circuit.

The invention has for itsv object to overcome the above-mentioned diiiiculties of compensation. To this end the nely divided ,magnetizable core to be moved into' a coil -is'so designed that the compensation is eifected by varying the magnetic property of the portion of the core which is to be inserted in the eld of the coil. Such a variation may, for instance, be obtained byvarying the cross-sections of the core or by employing diierent quantities of electrically conducting or magnetic material at diiferent40 points along the portion of the core to be moved into the coil. This may' be accomplished in the manner that the quantity of core material is reduced at certain points. To this end, slots extending transversely to the magnetic axis are arranged in the core. 'Ihe slots bring about a I. reduction of the cross-section of the core and thereforea decrease in inductance A similar effect is attained by placinga greater amount of electrically conducting material in the core, 50

providedthat this material is a diamagnetic substance. In this case the decrease in inductance is due to the field displacement within the core by the formation of eddy currents. To increase the inductance it is preferable to apply to the surface of the core magnetizable material in the form of compressed iron powder.

When compensating, the magnetizable core is inserted stepwise into the coil windingand the inductance isgiven the corresponding value by adding or removing as the case may be the above-mentioned compensating material. In this manner irregularities in the core material, structure and the like along the magnetic axis are compensated for. The compensating material may have the same permeability as the magnetizable core. A material of different permeability is, however, also applicable. If, for instance, a compensating material of higher permeability than that of the core is used, a very effective compensation may be obtained by means of a small amount of material.

Further details of the invention will be apparent from the following description taken in connection with -the accompanying drawing in which Fig. 1 is a sectional view of a core according to the invention.

Fig. 2 is a longitudinal view showing a modification of the invention.

Fig. 3 shows a similar view of a third embodiment,l and Fig. 3a one of a number of magnetic bodies serving to adjust the core of Fig. 3.

Fig. 4 is a longitudinal top view, Fig. 4a a transverse section and Fig. 4b a longitudinal section of a fourth form of the invention.

Fig. 5 shows a longitudinal section and Fig. 5a a transverse section of a fifth magnet core, according tothe invention. 1

Figs. 6 and 7 are longitudinal views of two other embodiments of the invention.

Fig. 8 is a longitudinal section through an ar-v rangement according to the invention in which, a core according to Figs. 3a and 3b is provided with a coil.

Fig. 9 shows a sectional view of a coil with a core similar to that of Fig. Sw.

Fig. l0 represents another embodiment consisting of a coil and a core of a construction similar to that of Figs. 4a, 4b and 4c.

In Fig. 1 is shown a bar core E which may tion of the magnetizable core I to be effected at the individual points. Accordingly, the groove-shaped recesses 2 are more or less iilled up by the compensating bodies 3 as will be seen from Fig. 1. s

In the embodiment of Fig. 2 also showing a magnetic core serving toA vary the inductance of -a coil, magnetizable or other metal bodies 5 In the form of the invention according tov Figs. 3 and 3a the compensation of the crosssection of the magnetizable core 6 is eiiected by metallic or magnetizable pins 8 which are placed into the holes 1. In order to eiiect an accurate compensation it ispreferable to thread the holes I as well as the pins 8 so that the desired depth of immersion may be exactly regulated by the screwing in of the pins. Also in this case the holes'l are arranged along the axis of the magnetizable core 9 so that an accurate compensation of the inductance may be attained at every position of the core with respect to a coil winding by varying the cross-section of the core 6.

'I'he greater the number of the recesses and of the compensating bodies provided in the forms of the invention shown in Figs. 1 to 3a the more accurate the inductance characteristic of coils may be adjusted and therefore also the gauging of the coils.

In the modification illustrated by Figs. 4, 4a and 4b the core 9 is provided in the direction of the magnetic axis with a groove-shaped recess I0 in which the magnetizable bodies II may be slidably mounted. The bodies II may have a dove-tailed cross-section in order to prevent a falling out of the bodies from the groove I0.. In this case the compensation is eiected by varying the distance of the mutual magnetizable bodies II. As will be seen from the Figures 4a and 4b the bodies are designed in such `a manner that they iill up completely the groove-shaped recess I0 in the vertical direction, whereas*v their length may be diierently dimensioned. Depending upon tage that when using tools in the form of trowels portions thereof may be again removed or applied to other points sothat in this manner the crosssection of the core may be compensated very exactly. Hot tools are preferably employed for thermoplastic substances.

Since in the case of cores which are to be in- ,serted in coil windings, it is preferable not to vary the dimensions of the core, the magnetizable substance employed for compensating the crosssection of the core is arranged preferably inl a longitudinal groove I3 of the core I4 as is shown in Figs. 5 and. 5a. The magnetizable substance isvdenoted by the numeral I5 and fills up the groove I3 more or less completely. When using a thermoplastic material the amount of the magnetizable substance, by means of a hot-trowel, may be yvaried at will at the individual points at which a compensation is to be effected.

According to another form of the invention the compensation of the cross-section of the magnetizable core may be eiiected by a thin sheet of a variable width or cross-section arranged along the magnetic axis. In this case the sheet consists of magnetizable material. for instance of iron, and is placed on the surface of the core. Such an embodiment is shown in Fig. 6 in which I'I denotes a bar'core on which is placed a strip I8 of sheet iron. The strip of sheet iron is slotted transversely with respect to the longitudinal axis as indicated at I9, so that the length of the teeth 29 may be varied by cutting the same so that the effective core cross-section may be adjusted at the individual points at which according to Figs. 5 and 5a.

With coil arrangements Whose slidable core is pot-shaped, the compensation of the core crosssection may be eiiected for the sake of simplicity on the outer jacket as is shown in Fig. 8, instead of on the core portion projecting into the interior of the coil. 24 denotes the cylindershaped coil winding arranged over the inner core portion 25 having also the form of a cylin' der, whereas the outer core portion forms a jacket 26 enclosing the coil winding 24. The magnetizable substance 21 for-compensating the cross-section of the core is placed as shown in Figs. 5 and 5a ina groove-shaped recess 28 which extends in the direction of the magnetic circuit of the core i. e. in the present embodiment in the longitudinal direction of the outer cylindershaped core portion 26.

The use of a core designed in a manner corresponding to Figs. 3 and 3a in a variable self-induction coil is shown in Fig. 9. 'I'he inductance of the'col 29 designed, for instance, in the form of a cylinder, is varied by moving the straight core 6 more or less into the coil 29. Over the surface of core 6 are distributed apertures 1 for compensating screws 8 with the aidl of which the effective .cross-section of the core may be adjusted. VThe screws 38 arranged at the ends of the core 6 engage in corresponding borings of the core 6 and serve to adjust the initial and final values of the inductance of the coil within shown a variable self-induction coil 33 which as well as the adjustable magnetizable core 9 has by a rotary movement. To this end, the core 9' the shape of a .circular arc. The core, otherwise. is constructed in the same Way as the core shown in Figs. 4, 4a and 4b. I'he arrangement of Fig. 10 has the advantage that it requires only small space and that the core 3 may be easily adjusted is secured to a lever 35 pivoted at an axis 36 which when rotated moves the core 9 into the coil winding 33.

What is claimed is:

1. In a variable inductance device having a coil and a magnetic core movable relative to each other, said core comprising a core body having a magnetic cross section smaller than that required for a desired inductance characteristic of the device, said core body having its peripheral surface recessed along the direction and over substantially the entire extent of said relative movement, and additive magnetic means disposed at said recessed surface and distributed over substantially said entire extent so as to adjust the magnetic cross section locally at diiferent points along said core to said desired characteristic.

2. A magnet core comprising a comminuted core body having its magnetic c^ross sections smaller than ihose required for a given charac'-y teristic, said core body having a multitude of recesses disposed at its peripheral surface and distributed longitudinally as well as peripherally over a substantial portion of said surface, and a plurality of individual magnetic bodies arranged in said recesses and completingxthe total cross sections so as to adapt the core to said given characteristic.

3. In a variable inductance device having a coil and a magnetic ,core movable relative to each other, said core comprising a core body having a magnetic cross section smaller than that required for a desired inductance characteristic of the device, said core body having at its peripheral surface a groove extending .in the direction and over substantially the entire length of said relative movement, and magnetic means for completing said cross section, said means being arranged insaid groove and distributed over said length so as to adjust the core to said desired characteristic.

4. In combination with an inductance coil, a magnet core movable relative to said coil and comprising a comminuted core body having its magnetic cross sections smaller than required for a desired characteristic, said body having at its peripheral surface a longitudinal groove, and a plurality of individual solid bodies of magnetic material arranged in and distributed along said groove so as to compensate at a plurality of points the departure of the permeability from said desired' characteristic.

ADOLF WEIS. 4

GNTHER DREWES. 

